1. Field of the Invention
The present invention relates generally to a communication system, and more particularly to a system and a method for generating a group messaging session in a communication system.
2. Description of the Related Art
In general, a Session Initiation Protocol (SIP) is a text-based application layer control protocol. The SIP is based on a client-server structure in which a server responds to calls of clients, and enables more than one participant to make, revise, and terminate a session together with each other. Further, the SIP is a protocol located above the User Datagram Protocol/Transmission Control Protocol/Internet Protocol (UDP/TCP/IP) and transmits/receives a message in a request/response manner.
SIP request messages include INVITE (an invitation to participate a session), ACK (acknowledgement to an invitation), BYE (session termination), REGISTER (registration of location information of a user client in a database of a register server), a CANCEL (cancellation of a waiting request), and OPTIONS (request for information from a server).
SIP response messages include status codes, such as 1xx (information response), 2xx (successful response), 3xx (re-direction response), 4xx (client error), 5xx (server error), and 6xx (area change error).
FIG. 1 illustrates a structure of a conventional SIP-based communication system.
Referring to FIG. 1, the SIP-based communication system includes a core network 120, and an SIP messaging application server (SIP application server) 100 and multiple application clients 140, 160, and 180. The multiple application clients 140, 160, and 180 communicate with each other through the SIP/IP core network 120.
The SIP application server 100 maintains and manages an SIP session for message transmission and reception between a transmitter-side SIP application client and a receiver-side SIP application client, and generates, maintains, and terminates a session of at least one SIP application client.
In order to support a messaging service of an SIP application client, the SIP/IP core network 120 registers an SIP application client and performs a routing function, that is, receives SIP messages generated for session generation, revision, and termination by an SIP application client and transfers the received SIP messages to the SIP application server 100 or the receiver-side SIP application client.
The SIP application clients 140, 160, and 180 are stationed at user terminals and perform a messaging service. That is, each SIP application client accesses a messaging service and generates, revises, and terminates the SIP session.
FIG. 2 is a signal flow diagram illustrating signal transmission and reception for session generation in a conventional SIP-based communication system.
Referring to FIG. 2, the SIP application client A 220 transmits an INVITE message for generating a session with SIP application client B 240 and SIP application client C 260 to an SIP application server 200 in step 201. In steps 203 and 205, the SIP application server 200 transmits the INVITE message to SIP application client B 240 and SIP application client C 260.
Upon receiving the INVITE message, SIP application client B 240 and SIP application client C 260 transmit a 200 OK message to the SIP application server 200, in steps 207 and 211, respectively. In step 209, the SIP application server 200 transmits a 200 OK message to the SIP application client A 220, as a response to the INVITE message received in step 201.
In the process described above, a session between the SIP application client A 220 and SIP application client B and SIP application client C 260 is generated. A more detailed description of the process illustrated in FIGS. 1 and 2 is disclosed in the Internet Engineering Task Force (IETF) Request For Comments (RFC) 3261 document.
However, the IETF RFC 3261 document does not disclose a scheme for generating a session in consideration of a capability of each SIP application client. That is, the conventional technology does not considered a group policy, which may operate as one of the mechanisms of authenticating users in generating a group messaging session.